The present invention relates to a Modified Maxillary Protraction Device (MMPD) designed for the treatment of growing skeletal and dental open-bite cases accompanied by maxillary development deficiency.
Since a long time, the treatment of skeletal Class III malocclusions only by using orthodontical methods has been accepted to be difficult and subject to obstinancy. Before the 1970's, Class III problems were defined mainly as mandibular prognatisms, and maxilla has not been very much emphasized in the literature. Later studies have shown that a real isolated mandibular prognatism constitutes only 20–25% of Class III cases.
According to Sinclair and Proffit (Sinclair, P. M.; Proffit, W. R.: Class III Problems: Mandibular Excess/Maxillary Deficiency, in Surgical-Orthodontic Treatment. (ed.) Proffit, W. R.; White, R. P. St. Louis: Mosby, 1991, CH. 14, p: 428–482.) among the Class III anomalies, 20–25% of the Class III population exhibited only maxillary deficiency, whereas 50–60% exhibited maxillary deficiency, together with mandibular prognatism. This rate increases up to 32–43% in the Japanese society wherein the incidence of Class III anomalies is quite high (Takada, K.; Petdachai, S.; Sakuda, M.; Changes in Dentofacial Morphology in Skeletal Class III Children Treated by a Modified Maxillary Protraction Headgear and a Chincup: A Longitudinal Cephalometric Appraisal, Eur. J. Orthod. 15:211–221,1993.).
Excessive vertical development of the mandible, as well as its excessive forwards development, is quite common in Class III abnormality groups and constitutes a combination that can be seen in 6% of the patients.
The treatment plan for a skeletal Class III open-bite patient, during his/her growth period, should be aimed at both saggital and vertical anomalies, and excessive vertical growth of the mandible must be prevented while the forwards-downwards growth of the maxilla is encouraged.
In the devices used in the state of the art, the forwards development of the maxilla is provided and the forwards development of the mandible is inhibited. However, with the usage of maxillary protraction appliances, as the downwards growth of the mandible is not prevented, the length of the face increases. This situation may lead to the ‘long-face syndrome’ wherein chin-face (craniofacial) surgical operations may be required in skeletodental open-bite cases. For such a surgical intervention, the patient has to wait until he/she is 18 years old or a multi-phase orthodontic treatment that may last for many years with separate applications for the maxilla and mandible, has to be employed. During the multiphase orthodontical treatment, first a reverse head gear is implemented in order to increase the forwards maxillar development, however, the vertical open-bite status cannot be controlled by this implementation. Therefore the open-bite treatment is postponed to a later phase and requires the use of a separate apparatus.
Some orthodontists deem it convenient to wait until the completion of the growth of the Class III open-bite patients, without any interventions and upon the completion of their growth, to employ surgical methods to correct such anomalies. In the state of the art, in EU Patent No. 445492, the mandible is connected to magnets fastened by means of correcting levers to a control box. However here, only a vertical force is exerted on the chin.
In Spanish Patent Application No. 97/43975, a similar device is disclosed, whereby only a force in the vertical direction is applied on the chin by using correcting elements. Furthermore, the correcting elements have no length adjustment and movement possibilities.
In both of these prior art devices, conformity to all types of patient faces cannot be provided.